From 0d6526f82c3cdefcca47f73f5fc08dc6f335eac6 Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Mon, 21 Sep 2026 17:37:22 -0700 Subject: sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling bug alb_break_llc() decides whether to break LLC preference during active load balance. It does so by testing that every runnable fair task on the source rq prefers its LLC: env->src_rq->nr_pref_llc_running == env->src_rq->cfs.h_nr_runnable But the two counters cover different sets. nr_pref_llc_running is updated in account_llc_enqueue()/account_llc_dequeue(), next to cfs_rq->nr_queued, so it follows queued tasks. h_nr_runnable is updated in set_delayed()/ clear_delayed() and drops delay-dequeued tasks. So under DELAY_DEQUEUE, a preferring task that goes to sleep stays counted in nr_pref_llc_running while h_nr_runnable falls. The equality then breaks, alb_break_llc() returns false, and active balance is free to pull a task off its preferred LLC. Active balance only moves runnable tasks, and this is the only LLC check it consults: once the stopper runs, LBF_ACTIVE_LB skips the per-task test in can_migrate_task(). The runnable set is the one we want. Fix it on the counter side. A task should be counted in nr_pref_llc_running exactly while it is both queued on its preferred LLC (pref_llc_queued) and runnable (!sched_delayed). Define that membership once in task_pref_llc_runnable(), and adjust the counter only through pref_llc_running_inc()/pref_llc_running_dec() from the four sites that change either input: account_llc_enqueue(), account_llc_dequeue(), set_delayed() and clear_delayed(). Gating every update on the same predicate keeps the delay, wake and dequeue paths from double-counting or underflowing; see the comments at those sites for the ordering. nr_llc_running and sd->llc_counts are not touched and stay on queued semantics. Fixes: 714059f79ff0 ("sched/cache: Handle moving single tasks to/from their preferred LLC") Closes: https://lore.kernel.org/lkml/20260827135000.735138-1-zhanxusheng@xiaomi.com/ Reported-by: Zhan Xusheng Suggested-by: Chen Yu Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Kayra Cizmeci Cc: # v7.2.x Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com --- drivers/rtc/rtc-ps3.c | 73 +++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 73 insertions(+) create mode 100644 drivers/rtc/rtc-ps3.c (limited to 'drivers/rtc/rtc-ps3.c') diff --git a/drivers/rtc/rtc-ps3.c b/drivers/rtc/rtc-ps3.c new file mode 100644 index 000000000..6b098734c --- /dev/null +++ b/drivers/rtc/rtc-ps3.c @@ -0,0 +1,73 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * PS3 RTC Driver + * + * Copyright 2009 Sony Corporation + */ + +#include +#include +#include +#include + +#include +#include + + +static u64 read_rtc(void) +{ + int result; + u64 rtc_val; + u64 tb_val; + + result = lv1_get_rtc(&rtc_val, &tb_val); + BUG_ON(result); + + return rtc_val; +} + +static int ps3_get_time(struct device *dev, struct rtc_time *tm) +{ + rtc_time64_to_tm(read_rtc() + ps3_os_area_get_rtc_diff(), tm); + return 0; +} + +static int ps3_set_time(struct device *dev, struct rtc_time *tm) +{ + ps3_os_area_set_rtc_diff(rtc_tm_to_time64(tm) - read_rtc()); + return 0; +} + +static const struct rtc_class_ops ps3_rtc_ops = { + .read_time = ps3_get_time, + .set_time = ps3_set_time, +}; + +static int __init ps3_rtc_probe(struct platform_device *dev) +{ + struct rtc_device *rtc; + + rtc = devm_rtc_allocate_device(&dev->dev); + if (IS_ERR(rtc)) + return PTR_ERR(rtc); + + rtc->ops = &ps3_rtc_ops; + rtc->range_max = U64_MAX; + + platform_set_drvdata(dev, rtc); + + return devm_rtc_register_device(rtc); +} + +static struct platform_driver ps3_rtc_driver = { + .driver = { + .name = "rtc-ps3", + }, +}; + +module_platform_driver_probe(ps3_rtc_driver, ps3_rtc_probe); + +MODULE_AUTHOR("Sony Corporation"); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("ps3 RTC driver"); +MODULE_ALIAS("platform:rtc-ps3"); -- cgit v1.3.1